1. Field of the Invention
The present invention relates to a sealed structure for an electronic device, and more particularly, to a sealed structure for a magnetic disk drive unit.
2. Description of Related Art
Electronic devices are typically built in such a way as to bring related components together in order to enable the device to function effectively, or, increasingly, to make the device as a whole more compact. In either case, the design or layout of the components is accommodated within a substantially rectangular or box-like housing. In such cases, depending on the type of electronic device involved the housing must often be sealed with a high degree of precision.
For example, in the case of a magnetic disk drive, in which the recording and reproduction of information to and from a rotary disk-like recording medium occurs in an interval between a surface of the disk and a magnetic head, that interval is very small, that is, on the order of microns. As the density with which information is being recorded to and reproduced from recording media continues to increase, head-to-disk intervals on the order of sub-microns are being sought.
The need for head-to-disk spacing accurate to the micron or sub-micron level means that any degradation in the quality of the seal of the magnetic disk drive such as would allow dust particles and the like into the interior of the device has the potential to disrupt the stability of the head as it floats over the surface of the disk, potentially causing the head and the rotating disk to come into contact with each other and causing head crashes and other undesirable events.
Thus, magnetic disk drives in particular require properly sealed structures. In order to further an understanding of the problem the present invention attempts to solve as well as of the invention itself, a description will now be given of the conventional magnetic disk drive sealed structure with reference to FIGS. 1 through 6.
FIG. 1 is a disassembled perspective view of a conventional magnetic disk drive. FIG. 2 is a partial perspective cross-sectional view of a conventional magnetic disk drive. FIG. 3 is a plan view showing a conventional magnetic disk drive prior to the installation of the cover. FIG. 4 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is properly mounted. FIG. 5 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing is deformed and protrudes beyond the contact surfaces. FIG. 6 is a partial cross-sectional view of a conventional magnetic disk drive, illustrating a case in which the packing has collapsed to one side.
As shown for example in FIGS. 1 and 2, a conventional magnetic disk drive 1 may have a disk-like recording medium (hereinafter disk or magnetic disk) mounted on a motor assembly not shown in the drawing, an actuator 4 that supports a head 3, and other electronic components not shown in the drawings, all mounted atop a base 5. The base 5 is in turn covered by a cover 6 having a substantially concave structure capable of accommodating the electronic components therewithin, the base 5 and the cover 6 forming a single unit.
In order to seal the space enclosing the actuator 4 and other electronic components inside the concave structure that is the cover 6, as shown in FIGS. 1 and 3, a thin sheet of packing 7 made of rubber and having a through-hole portion 7a corresponding to the concave shape of the cover is inserted between the cover 6 and the base 5, specifically between the respective contact surfaces 6a and 5a thereof. It should be noted that, in these and other diagrams, the packing 7 may be given a mesh design as necessary in order to distinguish it from other components.
When assembling the magnetic disk drive 1, for example, double-sided adhesive tape 8 cut to a shape identical to that of the packing 7 is adhered to the packing 7, such that the adhesive force of the tape 8 contacts the packing 7 against the flange-like contact surface 6a of the cover 6. The cover 6 is then positioned on the base 5 with the contact surface 6a facing downward, to achieve a state depicted in FIG. 4, which is essentially an enlarged view of a portion A of FIG. 2. Thereafter the cover 6 and the base 5 are formed into a single unit by a tightening member not shown in the diagram.
At this time, a restorative force generated by the compressive deformation of the packing 7 due to the tightening of the tightening member securely contacts the packing 7 against both the cover 6 and the base 5, thus sealing the actuator 4 and other components.
However, in the case of the magnetic disk drive 1 described above, for example as shown in FIG. 3, at points A and B the distances L1 and L2 from the outer edge of the disk 2 to the outer edge of the base 5 are small in comparison to other areas, as can be seen in FIG. 5. Reducing the distances L1 and L2 in this manner, however, is unavoidable if the intent is to make the magnetic disk drive 1 more compact.
However, at points at which distances are small, the widths W1 of the cover 6 contact surface 6a (the flange surface) and the base 5 contact surface 5a that contacts the contact surface 6a, which in turn means that widths W2, W3 of the packing 7 positioned between the base 5 and the cover 6 decreases as well. As a result, when positioning the cover 6 atop the base 5 a slight misalignment arises, such that when the packing 7 is compressed as shown in FIG. 5 the packing 7 protrudes beyond the flange-like contact surface 6a of the cover 6 and the contact surface 5a of the base 5. In this case, a predetermined restorative force of the packing 7 does not extend to the base 5 and the cover 6 and accordingly the seal formed by the packing 7 is inadequate and thus the sealing of the electronic components is also poor. Such lapses in quality can cause the packing to collapse to one side as shown in FIG. 6 or take on other extreme deformations, degrading the quality of the seal even further.
Accordingly, it is an object of the present invention to provide an improved and useful sealed structure for an electronic device in which the above-described disadvantage is eliminated.
The above-described object of the present invention is achieved by a sealed structure for an electronic device, the sealed structure comprising:
a base;
a concave cover enclosing electronic components of the electronic device when the cover is fitted to the base; and
a gasket-like sealing member that fits between edge portions of the cover and the base to seal the enclosure,
a rib portion being formed on at least one of either the cover or the base so as to prevent the sealing member from protruding from the edge portions of the cover and base.
According to this aspect of the invention, the sealing member can perform its designated sealing function because the sealing member can be prevented from protruding from the contact surface area, making it possible to provide an electronic device sealed structure with an improved seal.
Moreover, by providing the rib on either the inner periphery or the outer periphery of the sealing member, an improved seal can still be attained with relatively less processing of the rib as compared to a case in which ribs are provided on both sides of the sealing member.
Additionally, providing the rib on the outer periphery of the sealing member is advantageous in those areas where the contact surface area is restricted and it would therefore be difficult to provide a rib on the inner periphery of the sealing member. Moreover, providing the rib on the outer periphery restricts any protrusion of the sealing member outward therefrom, thus securely preventing degradation of the seal.
Additionally, by providing a rib at discrete, non-continuous, intermittent points along the periphery of the sealing member, an improved seal can still be attained with relatively less processing than is the case when the rib is provided continuously along the periphery of the sealing member.
In this case, providing the rib in such a way as to alternate between inner and outer periphery positioning, so that there is no overlap between the inner periphery and the outer periphery of the ribs, has the advantage of reducing the processing required to form the rib.
It should be noted that, in the sealed structure for an electronic device according to the present invention, by providing the rib at only those regions at which the contact surfaces are narrow (that is, the distance between the inner periphery and outer periphery is relatively small) and which can therefore be expected to be points at which the risk of the sealing member protruding outward from the structure is greatest, an improved seal can still be attained with only partial provision of the rib and thus with reduced processing as compared to a full rib extending the length of the periphery of the sealed structure.
It will be appreciated by those of ordinary skill in the art that such regions of reduced contact surface area can be determined easily as a matter of design.
Additionally, in the sealed structure for an electronic device according to the present invention, the side of the rib that contacts the sealing member has a slanted surface and the side of the sealing member that contacts the rib has a surface slanted in reverse to that of the rib, so that a deformation of the sealing member in a direction of a width thereof can be more securely restricted so as to provide an improved seal.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.